Rehabilitation of critical water main infrastructure for Sydney Water

Sydney Water Corporation (SWC) is arguably the largest water utility in the Southern Hemisphere and is highly regarded in Australia and around the world for innovative approaches to water management. In January 2017, Sydney Water approached Primus Line in regards to the rehabilitation of two critical trunk mains.

Trunk main rehabilitation

At Pymble in Sydney, a DN225 CICL main 47m in length under the Pacific Highway with 2×45 degree bends had to be renewed. This main developed a leak in the 1980s and, as no technical and commercially acceptable method of rehabilitation was known, the main was isolated, as traditional dig and lay was not possible given the critical nature of the Pacific Highway as a main carriageway.

In 2016, Sydney Water was informed that one of Australia’s largest retailers wanted to build a new outlet at this location and required a certain volume of water that would place a strain on the existing network. Sydney Water engineers noted the isolated DN225 and sought out trenchless solutions.

The solution was a DN200 PN40 medium pressure Primus Line®system. Given the congested nature of the Pacific Highway, all work had to take place between 9pm-4am. Once cleaning and CCTV were performed, the Primus Liner was pulled through the host pipe in one night.

Over in Penshurst, a DN300 CICL main 77m in length under a twin-track railway with 4×45 degree bends also had to be renewed. This main was damaged by a rail authority contractor over two years ago, and as a result was leaking.

As no technical and commercially acceptable method of rehabilitation was known, the main was isolated. Traditional dig and lay was not possible given the critical nature of the railway.

Sydney Water estimated that HDD was in the vicinity of over $600,000. The solution was a DN300 PN25 medium pressure Primus Line®system. This main was servicing a small retail area and a public amenities block, so all work had to be completed during the night as the main had to be isolated. After the cleaning and CCTV were performed the Primus Liner was successfully pulled through in one night.

The service life of these critical water mains was extended by at least 50 years. Sydney Water was able to renew both pipes in one week, including CCTV inspection, pipe cleaning, and liner installation. Cost savings in excess of 80 per cent could be realised compared to conventional methods.

Rehabilitation system

The client opted to renew the leaking water main with the Primus Line® system, a proven solution for the trenchless rehabilitation of pressure pipes. The AS/NZS 4020:2005 certified three-layer composite liner consists of a PE inner coating, a Kevlar® core to accommodate the operating pressure independently from the host pipe, and an abrasion-resistant PE outer layer to protect the Kevlar® core during the installation process.

The semi-structural solution is not bonded to the host pipe, can traverse bends of up to 45 degrees, and can be inserted in lengths of 1,000m and more in one single pull. Furthermore, due to the low wall thickness of only 6mm compared to corresponding HDPE pipes, the hydraulic capacity is only reduced minimally.